miR-451 Is a Driver of Lipotoxic Injury in Patients with Diabetic Cardiomyopathy.

MicroRNA 451 (miR-451) is emerging as a pivotal mediator of cardiac damage in experimental models of diabetic cardiomyopathy. Whether miR-451 plays a detrimental role in the human diabetic myocardium is unknown. The present study investigates miR-451's role in patients with type 2 diabetes (T2D). We show that miR-451 is upregulated in myocardial specimens from T2D patients compared to controls without diabetes and correlates with cardiometabolic parameters, the myocardial triglyceride content and cardiac expression of lipotoxic genes as well as echocardiographic indices of left ventricular dysfunction. Calcium-binding protein 39 (Cab39)-a known target of miR-451 in mouse hearts-was downregulated in T2D patients vs. controls, and its expression negatively correlated with that of miR-451. In cultured human cardiomyocytes (CMs), Ago2 immunoprecipitation confirmed Cab39 to be a direct target of miR-451. Treatment with a high amount of glucose (25mM) and palmitic acid (PA) mimicked miR-451 upregulation and Cab39 downregulation in human CMs. These changes were associated with increased TGs and markers of lipotoxic injury, such as elevated oxidative stress levels, mitochondrial dysfunction and apoptosis. Targeting miR-451 led to restoration of Cab39 levels while rescuing diabetes-induced lipotoxic injury and metabolic dysfunction. By contrast, miR-451 overexpression recapitulated features of lipotoxic damage. Our findings indicate miR-451 to be a potential target for the prevention of myocardial lipotoxic injury in diabetes.